Treatment of silica coated fibers



y 9, 1961 J. w. SCHAPPEL 2,983,625

TREATMENT OF SILICA COATED FIBERS Filed Feb. 20, 1957 DEPOSIT SILICA PARTICLES ON FIBER WATER RINSE FIBER APPLY FINISH TO FIBER DRY FIBER POLYHYDROXY ALCOHOL- FATTY ACID ESTER FINE SILICA PARTICLES I:

CELLULOSE FILAMENT 3 POLYOXYALKYLENE MODIFIED FINISH MATERIAL 2,983,625 TREATMENT on snrca COATED FIBERS Joseph W. Schappel, Morton, Pa., assignor to American Viscose Corporation, Philadelphia, Pa., a corporation of Delaware Filed Feb. 20, 1957, Ser. No. 641,244

18 Claims. ((31. 117-76) The present invention relates to the treatment of cellulose products for improving their resistance to soiling and more particularly relates to the treatment of regenerated cellulose products containing a deposit of'silica thereon.

It has heretofore been suggested to coat regenerated cellulose products and more particularly filaments and staple fibers of viscose rayon to deposit thereon finely divided silica to improve their resistance to soiling. The deposited silica, particularly that deposited on the outer surface of the fiber and not in the fiber crevices, has a tendency to become disassociated from the fiber during opening, carding, drawing, or other such mechanical operation where the coated fibers rub one against the other. This results in a fine dust which is objectionable. Various methods of depositing the silica on the cellulose have been developed for obtaining a firmer bond between the cellulose and the silica deposit. However, particularly withheavier deposits of silica, there is still a tendency for the silica on the outer surface of the filaments, not held in the crenulations, to become dislodged through frictional rubbing with adjacent coated filaments during mechanical working. Since it is the presence of the silica coating which improves the resistance of the fibers to soiling, it is generally desired to maintain as heavy a coating on the filament as can be maintained without appreciable dusting on later handling of the treated fiber.

It is also the general practice to treat regenerated cellulose fibers with finishing agents to improve the cardability and drafting of the filament, to soften the filament andto generally give the filament an improved hand or feel. Finishing agents suitable for this purpose and presently used by the trade include sorbitol monopalmitate or monolaurate with suitable emulsifying agents, and stearic acid modified withethylene oxide in ratios of about 80 to 150 ethylene oxide units per stearic acid molecule. However, when these finishing agents are applied to'fibers having asilica' coating, the problem of dusting is aggravated and the tendency to dust on later mechanical working is increased so that even fibers that would otherwise be acceptable from the standpoint of dusting may be rendered unacceptable, the finish coating apparently decreasing the bond between the silica and the fiber so as to make the silica more readily removable in later mechanical Working.

It has now been discovered that if the fiber containing the silica deposit thereon is treated with alkylene oxide adducts of polyhydroxy alcohol esters of higher fatty acids, not only is the fiber substantially improved with respect to carding, drafting, softness and hand or feel, but the amount of silica retention without dusting for any particular method of depositing the silica on the fiber is substantially increased.

This invention contemplates the use of polyalkylene oxide adducts of fatty acids esterified with polyhydroxyalcohols, as for example, the ethylene oxide and propylcue oxide adducts of such esterified fatty acids. The

tatcs Patent F Eatented May 9, 1961 products, suitable for the present invention, are found to melt within a temperature range of about 28 to 45 C. The preferred finishes melting within a range of 35 to 45 C. It is obvious that for all practical purposes considering cost, ease of preparation and commercial availability, the polyoxyethylene oxide compounds are preferred. Accordingly, the invention will be illustrated by reference to polyoxyethylene adducts of polyhydroxy alcohol esters of fatty acids. As is well known, the substances as commercially prepared generally are not pure compounds but consist of a group of mixed ethers and esters and may be prepared by reacting ethylene oxide with the esterified fatty acids. The substances, therefore, generally do not have a sharp melting point. The above temperature limits, therefore, actually indicate the temperature at which the molten substance first tends to set up or solidify on cooling from a higher temperature.

Where the polyoxyethylene modified polyhydroxyalcohol esterified fatty acids are mixed with other finish components, it is important that the composite finish component also have a melting temperature Within the range specified. If the temperature appreciably exceeds the 45 C. upper limit silica retention is substantially reduced. If it drops much below the 28 C. limit the improved resistance to soiling which is provided by the silica is appreciably reduced and, as finishes with lower melting points are used, the ease of soiling is increased.

The higher fatty acids contemplated for use contain from 8 to 1-8 carbon atoms, preferably from 15 to 17 carbon atoms. The esters may be prepared. from a relatively pure acid within the range or they may be prepared from technical grades of the acids or a mixture of the acids as derived from naturally occurring fats and oils suchas cottonseed oil, coconut oil, corn oil, soya bean oil, palm oils, peanut oil and the like and the hydrogenated fats and oils, the hydrocarbon chains being of the same number of carbon atoms as the fatty acids in ,which they have their origin. The polyhydroxyalcohol which is esterified with the acid may be any water-soluble polyhydroxyalcohol such as sorbitol, mono, di and triethylene glycol, erythritol and 1,1,1 trimethylol ethane.

The polyoxyalkylene or polyoxyethylene content of the adducts may vary from about 15 to 40 and more alkylene oxide units per molecule of polyhydroxyalcohol fatty acid ester, the preferred finishes containing from about 20 to about 30 ethylene oxide units per molecule. The finishes may be uniform in respect to the ethylene oxide chain or the substance may consist of a mixture of ethers having ethylene oxide chains of dilferent length depending upon the method of preparation. It is to be understood that for the purposes of this invention each of the chains of ethylene oxide units need not be identical.

The preferred finishes are prepared from fallow which is first treated, by any suitable means, to release the fatty acids therefrom which are in turn esterified with sorbitol. The resulting esters are reacted with ethylene oxide to give polyethylene oxide adducts of sorbitol fatty acid esters having 20 to 30 ethylene oxide units per molecule. These generally melt within the range of about 32 to 37 C.

Treatment of silica coated fibers with the polyalkylene oxide adducts of polyhydroxyalcohol esters of fatty acids in accordance with the present invention gives to the treated fiber an excellent hand or feel as well as sub stantially improving the silica retention during working. This is well illustrated by the following table showing the decrease in dusting obtained through the use, as finishes, of polyethylene oxide adducts of sorbitol tallow acid esters of varying number of ethylene oxide units in the molecule as compared with other finishing materials and silica-coated fiber having no finishing treatment.

Silica Eaten-- tion During Scouring Silica Retention Sample Finish 7 During Working 30% to 40% silica retention.

substantial dusting during carding and opening.

No finish do 1 Do.

do Do.

No dust observed during carding or working.

50% to 60% silica retention.

do Do.

In obtaining the results tabulated in the above table, a 15 denier yarn having a silica deposit of 0.7 percent silica by weight was used. The yarn was separated into different batches which were each treated with an aqueous emulsion of different finishing material, sample 1 not receiving any such treatment. Both finishing materials of the present invention, samples 5 and 6, and other finishing materials were used. Each of the samples was treated by immersion for 5 minutes in an aqueous emulsion containing 0.4 percent of the finishing agent. The yarn was then passed through nip rolls to remove excess emulsion and dried. The dried yarn was mechanically worked in an intense beam of light for determining dusting. Dust was noted with samples 1 through 4. No evidence of dust appeared in testing samples 5 and 6. 1

In practicing the present invention, it is generally preferred that the fiber containing the silica deposit be treated with the finish prior to drying, however, if desired, the fiber with the silica finish may first be dried and the fiber containing the silica coating then treated. with the finish. The finish is applied as a dilute liquid either in the form of a solution or an emulsion. Where the finish is applied to the fiber after it has obtained the silica deposit but before drying, the fiber is preferably given a water rinse and then passed through squeeze rolls between the silica treating bath and the finish bath so as to avoid contamination of the finish bath. After application of the finish, the fiber is again squeezed and dried. generally at a temperature of between 50 and 110 C. Figure l of the drawing is a diagram of the preferred treating steps for the process of this invention.

Figure 2 of the drawing is a partial cross-sectional enlarged view of a filament having silica particles deposited on the surface and in the crenulations, and polyoxyalkylene modified polyhydroxy alcohol-fatty acid ester finish coating the surface and deposited in the crenulations of the filaments.

The finish is preferably applied in the form of an aqueous emulsion. It is also generally preferred to .include in the emulsion a small amount of a cationic material. The cationic material helps to drive the finish,

which is non-ionic in nature, onto the fiber and also serves as a fiber plasticizer. Apparently, any cationic material that is compatible with the fiber and the finish may be used. Examples of some suitable cationic materials are Avitex R, a high alkylamine cationic softener sold by E. I. du .Pont de Nemours and Company; Ahcovel A, a fatty carbamide softener sold by Arnold Hoffman and Company; Arquad ZHT, a dialkyl quaternary ammonium chloride having the formula (R) N(CH Cl wherein the alkyl groups represented by R are made up of about 30 percent hexadecyl and percent octadecyl radicals sold by Armour and Company; and G-263, cetyl ethyl morpholinium hydrochloride, sold by Atlas Powder Company.

Where the finish is applied in the preferred manner, that is, together with a cationic material, the finish in the treating bath is generally present in amounts of 0.1 to 0.5 percent and preferably present in amounts of 0.2 to 0.4 percent. While the cationic material may be present in amounts of 0.05 to 0.2 percent and is preferably present in amounts of 0.10 to 0.15 percent. Where the cationic material is absent from the treating bath, the finished material should be present in larger concentrations and in such a case, should be present in amounts of- 0.3 to 0.6 percent. The preferred practice, however, isto; apply the finish from a bath that also containsa cationic material. The temperature of the finish bath may be any suitable temperature though temperatures of about 45 C. are generally preferred in practice. The fiber, after treatment, generally contains about 0.2 to 0.4 percent of the finish based on the total weight of the treated fiber.

The silica may be applied to the filaments, fiber, yarn, etc., in any suitable manner whereby the silica is deposited on the surface and in the fiber crenulations. In the preferred practice, however, the silica is deposited in the form of grown aggregates of silica containing a multivalent metal ion as described in copending applications, Serial No. 628,965 and Serial No. 631,415, new Patent No. 2,928,754. The grown silica aggregates are obtained by adding to a silica sol, of substantially-smaller silica particle size, a soluble salt of a multivalent metal. Where the silica deposit is obtained in this manner andthe silica-coated fiber then treated with a finish of the present invention as described, a fiber is obtained that has an excellent resistance to soiling over long and extended periods of use including numerous washings. Forthe best results, however, the silica-coated fiber, prior. to treatment with the finish, should preferably contain about 0.5 to 1.0 percent by weight silica and should generally not exceed 2.0 percent silica. Silica deposits of less than 0.3 percent are generally not suitable for satisfactory resistance to soiling.

The practice of the invention is further illustrated by the following examples which are given for the purpose of illustration only. The invention is therefore not limited thereto.

- Example] A 15 denier bright crimped viscose rayon staple was treated with a 0.2 percent SiO; solution prepared from colloidal silica, basic aluminum formate and barium' chloride as described in copending application, Serial No. 631,415, now Patent No. 2,928,754. Treatment was carried out under conditions which resulted in 0.7 percent SiO exhaustion on the fiber. The fiber was rinsed with water, squeezed and separate samples treated with soft finish aqueous baths of the following compositions:

Percent 20 dendro Percent Bath sorbitol Arquad 2HT esterlfied stearic acid tallow acids aesaoae checked for dusting, hand, and processability through carding.

.Sample Dusting Hand Processebility Slight dusting..- Harsh-Scroopy Poor. do SLHarsh-Scrci0p Do.

- do Fair.

S1. soft-Scroopy- Good. S1. soft-very Scroopy... D0.

Soft-Seroopy Excellent. Very soft-Scroopy Good.

Example 2 Tallow was hydrolyzed to yield free fatty acids having carbon chain lengths of C to C These acids were esterified by reaction with sorbitol and the ester was ethoxylated to various degrees to yield products having an average of 20, 30 and 40 ethylene oxide groups per sorbitol molecule. These products were applied to 15 denier viscose rayon staple containing 0.9 percent Si0 from aqueous 0.4 percent concentration baths at 45 C. The properties of the finishes and the treated fiber is tabulated below.

Average M.P. of Fiber Properties EtO/ Finish, Dusting Finish Sorbitol 0.

Hand Processing 1 82 None.-- Soft-Very Satisfoactory.

Scroopy. 2 30 38 do SoIt-Scroopy. Do. 3 40 44 Slight--. do Fair.

Example 3 Stearic acid was esterified with (1) glycerol and (2) sorbitol. Both esters were ethoxylated with an average of EtO groups per polyhydroxyalcohol residue. These products were emulsified in water to concentrations of 0.2 and 0.4 percent and applied to 15 denier carpet rayon pretreated with 0.6 percent SiO Treatment with finish was made at 45 C. for 6 minutes. The fiber was squeezed and dried at 100 C.

The properties of the finishes and treated fibers are tabulated below.

For convenience in the examples the ethylene oxide units per molecule are referred to by the term dendro. Thus, a stearic acid and glycerol ester containing on the average 25 ethylene oxide units per molecule is referred to as 25 dendro stearic acid and glycerol ester.

While preferred embodiments of the invention have been disclosed, the description is intended to be illustrative and it is to be understood that changes and variations may be without departing from the spirit and scope of the invention as defined by the appended claims.

Having thus described my invention, I claim:

1. In the treatment of cellulose fibers which have been silica-coated in order to increase their soil resistance, the improvement which comprises depositing on said fibers from about 0.2 to about 0.4% of a polyalkylene oxide modified polyhydroxy alcohol-higher fatty acid ester starting to melt within the range of about 28 to 45 C.

2. The improvement of claim .1 wherein said polyalkylene oxide is polyethylene oxide.

3. In the treatment of cellulose fibers which have been silica-coated in order to increase their soil resistance, the improvement which comprises depositing on said fibers from about 0.2 to about 0.4% of a finish comprising a polyethylene oxide modified polyhydroxy alcohol-higher fatty acid ester in which the fatty acid has a carbon content of 8 to 18 carbon atoms and which contains 15 to 40 ethylene oxide units per molecule.

4. The improvement of claim 3 wherein the finish starts to melt at a temperature within the range of 35 to 45 C.

5. The improvement of claim 4 wherein said polyhydroxy alcohol is sorbitol.

6. The method of claim 4 wherein the finish is an aqueous emulsion of said polyethylene oxide modified polyhydroxy alcohol-fatty acid ester.

7. The method of claim 6 wherein said polyethylene oxide modified polyhydroxy alcohol-fatty acid ester is present in said aqueous emulsion in amounts of 0.1 to 0.6 percent by weight.

8. The method of claim 6 wherein said polyethylene oxide modified polyhydroxy alcohol-fatty acid ester is present in said aqueous emulsion in amounts of 0.1 to 0.5 percent by weight together with 0.05 to 0.2 percent by weight of a cationic material.

9. The method of claim 8 wherein said polyethylene oxide modified polyhydroxy alcohol-fatty acid ester is a polyethylene oxide modified sorbitol ester of tallow fatty acid.

10. The process of improving the soil resistance of regenerated cellulose fibers comprising depositing a coating of about 0.3 to about 2.0% by weight of silica on said fibers and thereafter treating said fiber with an aqueous emulsion of a polyethylene oxide modified polyhydroxy alcohol-fatty acid ester melting at a temperature of about 35 to 45 C. and in which the fatty acid has a carbon content of 15 to 17 and which contains 20 to 30 ethylene oxide units per molecule, said polyethylene oxide modified fatty acid being present in said treating emulsion in amounts of 0.2 to 0.6 percent by weight.

11. The process of claim 10 wherein said silica deposit is obtained by treating said fibers with an aqueous suspension of grown silica aggregates.

12. The process of claim 11 wherein said polyethylene oxide modified polyhydroxy alcohol-fatty acid ester is polyethylene oxide modified sorbitol ester of tallow fatty acids.

13. A cellulose fiber having deposited thereon from about 0.3 to about 2.0% by weight of a silica coating in order to improve the soil resistance of said fiber, and having superimposed thereon a coating comprising from about 0.2 to about 0.4% by weight of a polyethylene oxide modified polyhydroxy alcohol-higher fatty acid ester melting within the range of 28 to 45 C.

14. The product of claim 13 in which the fiber is a regenerated cellulose fiber.

15. A soil resistant cellulose fiber having deposited thereon 0.5 to 1.0 percent by weight silica and having superimposed thereon from about 0.2 to about 0.4% by weight of a thin coating of a polyethylene oxide modified polyhydroxy alcohol-fatty acid ester melting at about 28 to 45 C. in which the fatty acid has a carbon content of about 8 to 18 carbon atoms and which contains 15 to 40 ethylene oxide units per molecule.

'16. The product of claim 15 in which said fiber is a regenerated cellulose fiber.

17. A soil resistant cellulose fiber having deposited thereon 0.5 to 1.0 percent by weight silica and having superimposed thereon from about 0.2 to about 0.4% by weight of a thin coating of a polyethylene oxide 7 modified sorbitol ester of tallow fatty acids containing iibout 15 to 40 ethylene oxide units per molecule.

18. The product of claim 17 wherein the polyethylene oxide modified sorbitol ester of tallow acids c'ontains'20 to 30 ethylene oxide units per molecule and starts to 5 melt within the temperature range of 35 to 45 C.

References Cited in the file of this patent UNITED STATES PATENTS 2,461,043 Eisen Feb. 8, 1949 ?8 Skalkees; Mar; 25, 1952 Jefferson et al. Feb. 9, 1954 Schlatter -5--- Sept. 28, 1954 Florio et al. Feb. 14, 1956 Maeder et al. Apr. 3, 1956 Ca 'oselli July 10, 1956 McLaughlin et a1. Apr. 30, 1957 Lange Apr. 30, 1957- Ewing Sept. 2 10, 195.7 

13. A CELLULOSE FIBER HAVING DEPOSITED THEREON FROM ABOUT 0.3 TO ABOUT 2.0% BY WEIGHT OF A SILICA COATING IN ORDER TO IMPROVE THE SOIL RESISTANCE OF SAID FIBER, AND HAVING SUPERIMPOSED THEREON A COATING COMPRISING FROM ABOUT 0.2 TO ABOUT 0.4% BY WEIGHT OF A POLYETHYLENE OXIDE MODIFIED POLYHDROXY ALCOHOL-HIGHER FATTY ACID ESTER MELTING WITHIN THE RANGE OF 28* TO 45*C. 